Seal for moving electron beam column



SEARCH ROOM Filed April 2, 1962 FIG. 2

x Z z w 4 a k 2 \\|I\ zr m 4 4 m 2 A a F 3 K fifl I. ,i w x Q Z W; d 4 Z/ Z I M/ 5 IQW/ Z 5 m f F li b C. f w H M /.l\ z WK x IN VEN TOR EDWARD W RADTKE Z &\ u.. By AGENT United States Patent 3,136,883 SEAL FOR MOVING ELECTRON BEAM COLUMN Edward W. Radtke, Bloomfield, Conn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Filed Apr. 2, 1962, Ser. No. 184,128 5 Claims. (Cl. 219-121) My invention relates to working a material with a beam of charged particles. More particularly, my invention relates to performing operations such as welding, cutting, melting, evaporating, or machining on any material with an electron beam.

The electron beam machines, as they are generally known, are devices which use the kinetic energy of an electron beam to work a material. US. Patent No. 2,793,281, issued May 21, 1957, to K. H. Steigerwald, discloses such a machine. These machines operate by generating a highly focused beam of electrons. The electron beam is a welding, cutting and machining tool which has practically no mass but has high kinetic energy because of the extremely high velocity imparted to the electrons. Transfer of this kinetic energy to the lattice electrons of the work piece generates higher lattice vibrations which causes an increase in the temperature within the impingement area suflicient to accomplish work.

It is Well known that pieces to be worked by an electron beam process must be placed in a region of low pressure. Working in the absence of gas is necessary for several reasons. First, any gas in the region surrounding the material being worked will cause impurities in the Work piece. Secondly, the presence of gas causes scattering of the electron beam, thereby preventing the precise focusing necessary to accomplish work at one spot without the material adjacent thereto being alfected by heat conductivity. Also, any gas present will cause rapid oxidation and thus destroy the electron emitting element of the machine. Prior to my invention, the size of the piece that could be worked with an electron beam was limited by the size of the vacuum chamber of the machine. That is, the piece to be Worked was placed on a movable table within the vacuum chamber of an electron beam machine and Work was performed by moving the table under the beam. With prior electron beam machines, therefore, the work piece size was limited to less than half the size of the vacuum chamber. For smaller parts, this restriction is acceptable but inconvenient. For larger parts, the cost of the vacuum chamber and associated pumps is so expensive that it becomes impracticable.

My invention overcomes the above disadvantages by providing apparatus and methods which permit working a piece as large as or larger than the vacuum chamber.

It is, therefore, an object of my invention to work materials with a beam of charged particles.

It is another object of my invention to increase the size of the piece that may be successfully worked by a beam of charged particles.

It is also an object of my invention to rapidly and inexpensively work large pieces with a beam of charged particles.

These and other objects of my invention are accomplished by creating a vacuum around at least a portion of a work piece and thereafter moving a beam generating apparatus along the length of the vacuum to perform the desired operation on the stationary work piece. My invention contemplates using a vacuum chamber having a slot the length thereof and sliding the beam generating means along this slot while maintaining the vacuum. The vacuum is maintained by a sealing means which travels with the beam generator and seals the slot both ahead of and behind the beam generator as it moves. After the moving column reaches the end of the slot, in

3,136,883 Patented June 9, 1964 one embodiment of my invention, the vacuum chamber is repositioned over the work piece thereby working successive portions of the work piece.

My invention may be better understood with reference to the accompanying drawing wherein like reference numerals refer to like elements in the different figures and in which:

FIGURE 1 is an end view of one embodiment of my invention.

FIGURE 2 is a side view of the embodiment illustrated in FIGURE 1.

FIGURE 3 is a top view of the vacuum chamber of the embodiment illustrated in FIGURE 1.

FIGURE 4 is an end view of a second embodiment of my invention.

FIGURE 5 is a side view of still another embodiment of my invention.

Referring now to FIGURE 1, an electron beam column is shown at 10. This column contains means, not shown, for emitting electrons, focusing the electrons into a beam and accelerating the beam toward a work piece. The beam formed in column 10 is shown at 12. The work piece, which may be two flat plates to be joined by a butt weld, is shown at 14, in a vacuum chamber 16. Chamber 16, as well as column 10, are evacuated by vacuum means pumping means, not shown, which are well known in the art. As shown in FIGURE 3, the top of chamber 16 contains an elongated slot 18 which is surrounded by a seal 20 which may be an O-ring. The column 10 has a sliding plate 22 attached thereto. The column and plate are positioned on the vacuum chamber 16 in such a manner that the beam of particles emanating from the column 10 passes through the slot 18 to impinge upon the work piece 14. The combined Weights of plate 22 and column 10 cause plate 22 to press against seal 20. The pressure exerted by plate 22 against seal 20 provides an air tight seal therebetween. When it is desired to weld work piece 14, the column and plate are caused to slide along slot 18. An air tight seal between plate 22 and seal 20 may be further insured by the use of vacuum grease. The grease will also facilitate movement of the column. As shown in FIGURE 1, the movement of the column 10 may also be eased by providing rollers or balls 24 which are attached to the column and which run in ways 26 in the top of the vacuum chamber. These balls or rollers allow an adequate squeeze on the seal while preventing rubbing of the plate against the chamber.

From the above, it can be seen that a work piece the length of the vacuum chamber can be operated on with a beam of charged particles by use of my invention. By attaching a plate 22, which is at least twice as long as the vacuum chamber 16, to the electron beam column 10 of the machine, and providing a seal 22 in the top of chamber 16, the particle generator can be moved the length of the chamber thereby permitting welding of pieces twice as long as could be welded with prior art devices or, conversely, permitting the use of vacuum chamber half as large as those formerly employed.

Referring now to FIGURE 4, there is shown a second embodiment of my invention wherein the vacuum chamber enclosing the work piece is eliminated. In FIGURE 4, the work piece 14 shown is the tank of a missile which has been formed by rolling a thin sheet into a cylinder. Because of the types of metal used and the thinness of the cylinder, electron beam welding is a very desirable method of joining the ends of the sheet to close the cylinder. However, because of the size of the cylinders, it is impractical to construct a vacuum chamber which would accept these pieces. The embodiment of FIGURE 4 utilizes a box or cup-like structure 40 which may be placed over a portion of the joint to be welded. Structure 40 is made to fit the contour of the work piece and Q) is sealed to the work piece by means of seals 42. The structure 40 is evacuated in the conventional manner to form a local vacuum in the area to be welded. The top of structure 40 has the same configuration as the top of the vacuum chamber shown in FIGURES 1 through 3. By use of the embodiment of FIGURE 4, a portion of the joint of the cylinder may be Welded, and then the structure 40 can be moved along the joint to weld successive portions thereof. It is, of course, understood that the joint itself must be sealed in the area not covered by structure 40 and the interior of the work piece must then be evacuated. This sealing may be accomplished by use of a pressure sensitive tape as taught in my copending application No. 183,096, filed March 28, 1962.

Referring now to FIGURE 5, there is illustrated another embodiment of my invention. The vacuum chamber of FIGURE 5 is similar to that discussed in relation to FIGURES 1 through 3 above. That is, the elongated slot for the beam is surrounded by a seal 20 and the beam forming column is supported on top of the chamber by wheels or rollers which run in ways in the top of the chamber. These ways and rollers guide the column so that it follows a straight line as it moves. Between the column 10 and the chamber 16 there is a strip of thin metal 50. This metal tape is attached to column 10 and is used to pull the column back and forth by means of a drive mechanism, not shown, on the tape reels 52 and 54 located at each end of the chamber 16. The pressure difference across the tape holds the tape against the top of the slot and the seal 20. The thickness of the tape 50 is chosen to be stiff enough to span the slot without excessive stress or deflection, and yet to be pliable enough to enable it to be wound up on the reels 52 and 54 without excessive stress. To minimize friction and Wear on the tape and seal, the parts are lubricated with vacuum grease in the same manner as the plate 22 of FIGURE 1 is lubricated.

While my invention has been discussed in terms of welding with an electron beam, other operations such as drilling, cutting and machining may be performed with the aid of my invention without deviating from the scope and spirit thereof. Also, while preferred embodiments of my invention have been shown and described, it is to be understood that my invention has been described by way of illustration rather than limitation and accordingly it is to be limited only by the appended claims taken in view of the prior art.

I claim:

1. Apparatus for working materials with a beam of charged particles comprising:

means for creating a low pressure environment about at least a region of a material to be worked, said means having an opening in the top thereof;

means for generating an intense beam of charged particles;

means movably supporting said beam generating means exterior of and aligned with a portion of the opening in the top of said low pressure environment creating means so that the beam of charged particles produced by said beam generating means may pass through the opening and impinge upon a material to be worked, said supporting means being in sealed relationship with said beam generating means and extending therefrom a distance at least equal to the desired range of movement of the beam generating means whereby the portions of said opening not under said beam generating means are covered by said supporting means regardless of the position of the beam generating means; and

means positioned between said supporting means and the top of said low pressure environment creating means for providing an air tight sliding seal around said opening.

2. Apparatus for Working materials with a beam of charged particles comprising:

means for creating a low pressure environment about at least a region of a material to be Worked, said means having an. elongated slot in the top thereof;

means for generating an intense beam of charged particles;

means movably supporting said beam generating means exterior of and aligned with a portion of the slot in said low pressure environment creating means so that the beam of charged particles from said beam generating means may pass through the slot and impinge on a material to be worked, said supporting means being in sealed relationship with said beam generating means and extending over said slot in both directions from the beam generating means a distance substantially equal to the length of the slot whereby the length of the slot not directly under the beam generating means is covered by said supporting means regardless of the position along the slot of the beam generating means; and

means positioned between said supporting means and the top of said low pressure environment creating means for providing an air tight sliding seal around the slot.

3. The apparatus of claim 2 wherein the supporting means comprises:

an apertured elongated plate having said beam generating means sealably mounted thereon in alignment with the aperture therein.

4. The apparatus of claim 3 wherein the means providing a sliding seal comprises:

a seal mounted on the top of said low pressure environment creating means and extending completely around the slot, said seal being adapted to be squeezed between said top and said elongated plate to thereby provide an air tight seal across which the plate may be caused to slide.

5. The apparatus of claim 4 wherein the low pressure environment creating means comprises:

a chamber having a slotted plate as the top thereof,

means for evacuating said chamber, and

I means for supporting the material to be worked in said chamber.

References Cited in the file of this patent UNITED STATES PATENTS 2,053,417 Brace Sept. 8, 1936 2,793,282 Steigerwald May 21, 1957 2,812,417 Busse et a1. Nov. 5, 1957 2,856,510 Jones et al. Oct. 14, 1958 2,950,378 Tuthill Aug. 23, 1960 

1. APPARATUS FOR WORKING MATERIALS WITH A BEAM OF CHARGED PARTICLES COMPRISING: MEANS FOR CREATING A LOW PRESSURE ENVIRONMENT ABOUT AT LEAST A REGION OF A MATERIAL TO BE WORKED, SAID MEANS HAVING AN OPENING IN THE TOP THEREOF; MEANS FOR GENERATING AN INTENSE BEAM OF CHARGED PARTICLES; MEANS MOVABLY SUPPORTING SAID BEAM GENERATING MEANS EXTERIOR OF AND ALIGNED WITH A PORTION OF THE OPENING IN THE TOP OF SAID LOW PRESSURE ENVIRONMENT CREATING MEANS SO THAT THE BEAM OF CHARGED PARTICLES PRODUCED BY SAID BEAM GENERATING MEANS MAY PASS THROUGH THE OPENING AND IMPINGE UPON A MATERIAL TO BE WORKED, SAID SUPPORTING MEANS BEING IN SEALED RELATIONSHIP WITH SAID BEAM GENERATING MEANS AND EXTENDING THEREFROM A DISTANCE AT LEAST EQUAL TO THE DESIRED RANGE OF MOVEMENT OF THE BEAM GENERATING MEANS WHEREBY THE PORTIONS OF SAID OPENING NOT UNDER SAID BEAM GENERATING MEANS ARE COVERED BY SAID SUPPORTING MEANS REGARDLESS OF THE POSITION OF THE BEAM GENERATING MEANS; AND MEANS POSITIONED BETWEEN SAID SUPPORTING MEANS AND THE TOP OF SAID LOW PRESSURE ENVIROMENT CREATING MEANS FOR PROVIDING AN AIR TIGHT SLIDING SEAL AROUND SAID OPENING. 